Not all of them mind you. Not William Nylander or Kasperi Kapanen, who aren't yet 20 but have been tearing up the American Hockey League with the Toronto Marlies. Not other promising youngsters such as Tobias Lindberg, Rinat Valiev and Connor Brown, either.

But with the Toronto Maple Leafs trading away three veterans in the past few days – and with six others on injured reserve – the influx of youth became especially apparent against the Nashville Predators on Tuesday night.

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Headline: The Toronto MarLeafs era has begun. With a hard-fought 3-2 loss.

That was expected, given the lineup. The Leafs' oldest defenceman on Tuesday was Jake Gardiner, at the grizzled age of 25. The third defence pairing was made up of two rookies – Stuart Percy and Viktor Loov – who were making only their 10th and third NHL appearances, respectively.

Among the Leafs' nine "vets," three had spent almost their entire season in the minors.

Everyone older than 25, meanwhile, is on the market in general manager Lou Lamoriello's grandiose garage sale, including both starting goaltender James Reimer and backup Jonathan Bernier.

Which makes one wonder: Exactly who will be in the lineup next Monday night against Tampa when the Leafs face the Lightning a few hours after the trade deadline?

Potentially more kids.

"Potential – that's like a dirty word if you don't do anything with it," Leafs coach Mike Babcock said of all the fresh faces joining his roster. "You've got to do something with it. Which kids are going to be NHL players and good NHL players? I don't have the answer for you. What we're going to do is we're going to bring them here, we're going to watch them and they decide."

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Predators coach Peter Laviolette's team is in a Central Division dogfight to make the playoffs, but he evidently wasn't terrified of the Leafs' makeshift roster Tuesday night. He rested captain Shea Weber (listed with a lower-body injury) and used backup Carter Hutton in goal. He also heaped minutes on former Leafs prospect Petter Granberg, who has played only seven games – averaging less than 13 minutes a night – since Nashville scooped him up on waivers in November.

None of that really seemed to matter in terms of the result.

Preds star Filip Forsberg scored early in the first and then twice in the second, putting up a natural hat trick in the game's first 26 minutes to force the reeling Leafs to chase it the rest of the way.

What the Leafs offered on Tuesday – and in the Leafs' remaining 24 games for that matter – was a preview of what next season might look like. While the Leafs came into this season with an older team (average age 28), that average was down by nearly two years against the Preds, and should fall even further still by October.

London Knights star Mitch Marner, who turns 19 in May, will have outgrown junior by next September and won't be eligible to play in the AHL. It only makes sense to start his NHL career. Nylander, too, will be ready for a bump up, perhaps along with whoever Toronto takes with its first-round pick in June.

The Leafs spent the bulk of this season with only one regular player (Morgan Rielly) who was under 24 years old. Next year, by the 2017 trade deadline, they could have half a team in that range.

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But there will have to be a balance there. Management has preached patience from the beginning of this rebuild. But the thing is, some of these Marlies look ready. Brendan Leipsic, for one, should be able to make the jump, as evidenced by his spot on the Leafs' top line against the Preds. Other older prospects such as Zach Hyman, Percy, Josh Leivo and Nikita Soshnikov should as well, even if it's as depth players.

In a league that keeps getting younger, turning 23 often means you're waiver-eligible, which means you're often getting a look.

"I'm just trying to show that I've developed into a player that can at some point next year challenge for a full-time job," Leipsic said. "It's what my focus is this year."

He isn't alone. Marlies coach Sheldon Keefe has been careful to counteract the "patience" message by telling his troops that when they are fully ready, they will be rewarded with a call-up to the Leafs. That's the carrot at the end of the stick for a team that has been annihilating the competition in the AHL.

Should they go on a long playoff run, more Marlies will expect at least a taste of what's next.

The youth movement may not pay off with Leaf wins. In fact, it probably won't – and there'll be more ugly nights against good teams such as Nashville. For all the intriguing prospects the Leafs have, there doesn't yet appear to be a No. 1 defenceman. There's no Connor McDavid, either.

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So expect growing pains and another playoff-less season or two. But at the very least, fans will be watching the future instead of a team of rental players awaiting their next destination.

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